Severe detonation up hill
Harley Tuner & High PerformanceDiscuss Severe detonation up hill in the Harley Tech & Harley How-to forums; Hey folks
Had an attack of the bursting marbles today. We were riding two up in bad traffic up a steep hill. Two up for us is still under 270 ...
Hey folks
Had an attack of the bursting marbles today. We were riding two up in bad traffic up a steep hill. Two up for us is still under 270 pounds so it's not like it was struggling under the load. Air temp was under 70 degrees so it wasn't over heating either. Each time I tried to inch forward with the cars it would begin to ping like crazy as the rpm lowered to a near lug with the clutch beginning to grab. I'd fire some gas in there with the throttle to bring up the revs while still trying not to go over the trunk of the car ahead of me. It would stop pinging as it reved but sure as hell made for a squirly few minutes till we crested the hill and it stopped. My wife asked "why is the bike trying to jump?"
Okay now the engine math.
I had a fresh tank of high test and trust the gas station where I bought it.
I am runing 30 degrees of advance at WOT 5000 rpm on a curve that starts out at 14 degrees at idle and 18 degrees at 2000rpm climbig to 22 at 3000rpm. I have no tach but figure the pinging stopped by 2000 so I wouldn't have reved any higher.
Air Fuel runs between 14 and 15 in that rpm range.
I have 10.25 to 1 compression.
My valve lift is .508
Intake duration 248 degrees
Exhaust is 256 degrees
Let me guess which head gasket is in there. Get all the specs and calculate dynamic compression. You may get relief with less advance but for now go for octane booster.
Location: Winston Salem, Greensboro area of North Carolina
Posts: 125
Re: Severe detonation up hill
It sounds like it was just too hot. The factory ECM lowers the idle as the engine gets hot. It lowers the idle alot more when the temperature is above 176 degrees.
The ECM is also programed to run the leanest between 176 - 262 degrees. If you are using a SERT, you can enrich the AFR at those temps. and you can also increase the idle at these temps.
A couple of years ago, I saw a Softail in a Christmas parade get so hot that smoke poured out the exhaust and then it stopped running. The outside temp was around 59 degrees.
It is a carb bike. ECM isn`t going to help the A/F ratio unless it has learned to use a screw driver. I agree it got too hot but why ? I see cops leave a bike running at accidents for way too long without detonation. Yes they have a cooling fan and different tuning. A performance module will retard the timing 5deg and might help but with that much duration having idle detonation and A/F over 14 means carb tuning or lower comp or more octane.
I am happy to see you don't have such a high final advance anymore like you did right after your build..
I always sugg No more than 30-32* final advance..
Remember, I time my 120" at 28*, same for the 127" and the 93" shovel & 80" at 30*..
In your case it is not "over-all" that is getting you.. It is your Rate of Advance.. If it pings on a 70 degree day,, grade or not,, 2-up or not,, you have your work cut-out for you..
Is there a reason it is 14* at idle.? What rpm do you idle at.?
Is it built in to your elect. Ign.? That's too much at idle, Twinky or not..
Everything I've learned over the years and the way I tune is to idle about 5-8* and finish at about 2200 - 2400 rpm..
Too fast rate of advance will enable detonation and Too much retard will overheat a motor, also enabling deton.. I think that's what is happening here.. Along with a lean condition..
Your pinging was caused by controllable factors now control them..
Consider fattening up that RPM range and try the timing I sugg..
BTW---- was it you that was thinking about getting a waaaay more grabby & heavy clutch..????? How do you think you woulda liked that today..???
__________________ "Fill your hands you son of a bitch"
Rooster Cogburn
I would agree with, frisco about the ignition advance numbers and all. But that was one hill. What does that thing run like without a hill situation?
If that bike likes the setup you have and it runs like spank, then I would not touch it since it was just one hill/traffic situation.
I am more, let it ping to advance and back it off 2° to set the timing right there is for me. So, it more or less looks like you are within that window of ping. Because you have not complained about your mod's performance... Just a one time situation, correct?
Cntrhub I can't let it be because I worry about my morning commute which is often in worse traffic and because I'm not wired that way. I'll worry it to death waiting for the next ping and that will take all the joy out of it for me. But you're right it works great as is and runs like the wind so I don't want to over correct either.
You guys have given me some things to try on the ignition and idle side. Idle may be why it overheated yesterday and not in traffic during commutes last year. I pulled the carb off to clean the jets and to lube the throttle cable mechanism during the winter and to run cable lube up as well as down the cables. I backed off the idle screw to get a slippery fussy cable back on once the carb was re-installed. I thought I turned it the same number of turns to get it back in place but noticed it is racing a bit at idle now. I thought very cold mornings in April so fast idle might be good and I did not bring it back for now. My bad, I'll do that today.
After the bike cooled down I went out alone and ran a brief full throttle roll on test in fourth gear. Slight detonation did occure in mid rpm to high where it did not ping last year. I will back the advance off as you suggest Frisco. Although the curves available with my ignition won't go as low as you suggest at idle, all are above 10 degrees.
As for the AFM running lean in that range Wrighturn it is an odd blip on the Dyno sheet and I am not sure how to correct it. It settles right on the line at the suggested ratio shortly after 2000 and stays there through the end of the run. A bigger slow jet might fix the off idle blip but would it hurt in the mid rpm range? I am considering a new bigger carb but have not yet convinced myself it is worth the money.
I will absolutely go bring the ignition back right now and adjust the idle screw.
I think you should and I do not know the ignition systems, so that right there has me re-posting once I hear what you have as your setup.
But think about this. I know that bike ran like the wind first off. So, now I have a hot rod for the weekend and a VOES piggybacked next to my other VOES. I have a vacuum pulling a lot more retard so I do not ping. I then swap on the (Wind Running VOES) wires where there are my two, 'Street-traffic/Wind Chaser VOESignals' that are, "On The Fly."
I have a T-Fitting off both VOES for vacuum. I just swap the purple wires from one VOES retard signal or use the other. I could even toggle switch them instead of pulling over and swapping the purples. I mean, there is the deal for me and how well my bike starts on one VOES and hooks the wind with the other.
So, if I knew your ignition unit, as in V=Vacuum or E=Electronic vacuum (without the use of the intake), etc. We have to start all over again with the way your unit retards and exploit it like I do with my Evo and VOES piggies.
What jets and needle are in the carb now ? A needle chang alone may solve your problem. By all means fix the problem. I can send you pistons that came out of "just let it ping " bikes. A slightly rich motor will run cooler longer. You can always go lean for dyno runs or whenever you feel like abusing the motor. The 14.7 is not in the best interest of an air cooled HD.
Severe detonation up hill 
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